In mobile communications networks, a variety of different mobile signaling protocols are used to route calls, obtain subscriber information, and deliver SMS messages to mobile subscribers. For example, in North America, American National Standards Institute (ANSI)-41 or Interim Standard (IS)-41 is the dominant application layer mobile signaling protocol. In Europe, the Global System for Mobile communications (GSM) protocol is the dominant application layer mobile signaling protocol. GSM is also being increasingly used in North America. In addition, Session Initiation Protocol (SIP) is a widely used Internet Protocol (IP) telephony signaling protocol primarily used for voice over IP calls.
In some networks, a mobile telecommunications service provider that was initially an IS-41-only service provider may desire to add GSM service. Alternatively, a GSM-only service provider may desire to add IS-41 service. In order to add a new type of service, the service provider must add signaling nodes, such as mobile switching centers (MSCs), visitor location registers (VLRs), and home location registers (HLRs) of the new service type.
In a network that includes GSM and IS-41 network elements, some mechanism must exist for ensuring that signaling messages relating to calls directed to IS-41 subscribers are delivered to the appropriate IS-41 network elements and that signaling messages relating to calls intended for GSM subscribers are routed to the appropriate GSM network elements. This problem becomes quite complex in a network in which some subscribers are IS-41-only, others have multiple subscriptions, and still others are GSM-only. In a situation where a subscriber adds a new service or migrates to a different type of service, the subscriber may desire to keep the same directory number (DN). Because the same DN can be associated with different subscriptions, the processing and routing of mobile signaling messages in such an environment becomes even more complex.
Conventional solutions to routing messages for calls from a subscriber of one application layer mobile signaling protocol to a subscriber of a different application layer mobile signaling protocol include simply converting each message from one application layer mobile signaling protocol to another application layer mobile signaling protocol and vice-versa. Converting each message from one protocol to the other protocol and vice-versa greatly increases the time required to set up calls and increases the number of signaling messages in the network. In addition, conventional protocol converters are incapable of giving priority to one service type for dual-mode subscribers (e.g., subscribers that have both IS-41 and GSM subscriptions with the same service provider) and properly routing calls to dual-mode subscribers.
Similar issues arise when considering the porting of subscribers from one service provider to another while keeping the same DN, otherwise known as number portability (NP). Ported mobile subscribers may either be “ported in” to an operator's network from a competing carrier, or “ported out” of an operator's network to a competing carrier. One problem associated with processing messages associated with ported subscribers is locating the correct HLR containing the subscriber's subscription information. Various solutions exist in which MSCs, HLRs, and STPs cooperate to locate mobile subscription information so that calls and SMS messages can be routed to mobile subscribers. However, these solutions are directed solely to processing signaling messages associated with ported subscribers and do not provide an efficient mechanism for processing signaling messages associated with migrated subscribers or dual-mode subscribers.
In many respects, GSM and IS-41 based networks are quite similar, with the primary differences between the two technologies simply relating to the protocols used to communicate between the various network entities, and the operating frequencies of the communication handsets themselves.
A conventional call routing scenario is illustrated in FIG. 1. FIG. 1 shows a signaling transfer point (STP) 100, an IS-41 MSC 102 and an IS-41 HLR 104 that provide IS-41-based services, and a GSM MSC 106 and a GSM HLR 108 that provide GSM-based services. In FIG. 1, the GSM and IS-41 components may be under the control of the same service provider or may be operated by different service providers. As shown in FIG. 1, STP 100 communicates with each of IS-41 MSC 102, IS-41 HLR 104, GSM MSC 106 and GSM HLR 108 via signaling links over a network infrastructure. Similarly, IS-41 MSC 102 and GSM MSC 106 communicate via signaling links over a network infrastructure. That is to say, all of the entities shown are nodes communicating via signaling links over one or more networks.
MSCs are generally identified as network switching elements. Among their many functions, MSCs are responsible for determining which cell site will take possession of a call. Such hand off control is facilitated by a communication link between an MSC and an associated Base Station Controller (BSC)/Base Transceiver Station (BTS) pair (not shown). In contrast, an HLR is, briefly stated, a database that is used to store subscriber information for all customers within the home service area of the service provider. Functionally, an HLR is linked through a signaling network to other service areas such that subscriber information may be efficiently shared between geographically diverse networks, a characteristic that facilitates seamless inter-network roaming. Like an HLR node, a VLR node is also a database that contains subscriber information. A VLR, however, is specifically used to store information related to subscribers who are not in their home service area. More particularly, a VLR is where roaming related data for a customer is stored when the customer activates their handset outside of their designated home service area.
As generally illustrated in FIG. 1, STP 100 is coupled via signaling links to two HLR database nodes 104 and 108, and as such, all signaling message access to the HLR database nodes is controlled and administered by STP 100. Within a GSM wireless communication network, each mobile station handset is assigned a unique identification number known as an International Mobile Subscriber Identity (IMSI) identification number. In the case of European GSM-type network implementations, the IMSI code is typically associated with a particular telephone handset. In such networks, each user can also be assigned one or more Mobile Station Integrated Services Digital Network (MSISDN) numbers. In the wireless telecommunications industry, MSISDN numbers are analogous to the 10 digit telephone numbers in a conventional North American wired network. The fact that multiple MSISDN numbers can be associated with a single IMSI number indicates that more than one MSISDN number can be assigned and used to reach a single mobile station handset. It should be appreciated that the term “Directory Number” (DN) is used generically herein to refer to IMSI, MSISDN, Mobile Global Title, ANSI-41 Mobile Identification Numbers (MIN) and Mobile Directory Numbers (MDN), and other identification numbers associated with subscribers or handsets in a wireless communication network.
In any event, an MSISDN number is dialed whenever a user wants to communicate with a particular GSM mobile station. Referring to FIG. 1, STP 100, by analyzing a part of the dialed MSISDN number, determines the particular HLR that is storing routing information associated with the called mobile station. It should be appreciated that, depending on the nature of the call or signaling event, an STP may analyze and direct an HLR lookup based on either the IMSI or MSISDN number associated with the called or calling party, but the term DN is used herein to refer to each of them.
In the signaling example illustrated in FIG. 1, an ISDN user part (ISUP) initial address message (IAM) message is sent to IS-41 MSC 102 in an attempt to establish a call to a mobile subscriber. Those skilled in the art of mobile communication networks will appreciate that an ISUP IAM message is one of many signaling messages that are employed in a signaling system 7 (SS7) based signaling network to facilitate the setup of a telephone call. A detailed discussion of SS7 signaling message types and their associated function can be found in Signaling System #7 by Travis Russell, McGraw-Hill Publishing 1998.
In response to the IAM message, IS-41 MSC 102 launches a location request (LocReq) 1 to determine the location of the called mobile subscriber. Those skilled in the art of mobile communication networks will appreciate that a LocReq message is one of many signaling messages that are employed in an IS-41 based signaling network to facilitate the setup of a telephone call. The LocReq message queries an HLR for, registration, routing and location information about the mobile station. A detailed discussion of IS-41 signaling message types and their associated function can be found in Mobile Telecommunication Networking With IS-41 by Michael D. Gallagher et al., McGraw-Hill Publishing 1997. Additionally, a detailed discussion of GSM related signaling within a network can be found in The GSM System for Mobile Communications by Michel Mouly and Marie-Bernadette Pautet, Cell & Sys 1992.
Returning to the discussion of FIG. 1, it will be appreciated that LocReq message 1 is received by STP 100, which in turn analyzes the message. More particularly, STP 100 examines the DN associated with the called party, as well as service indication information contained in the message. STP 100 performs a lookup in an HLR routing table, determines that this message should be delivered to IS-41 HLR 104, and subsequently forwards the LocReq message 2 to IS-41 HLR 104. Upon receipt of LocReq message 2, IS-41 HLR 104 examines the message and, in one case, determines that the DN has been migrated to GSM services. This determination is made via a lookup in an internal routing database of IS-41 HLR 104. IS-41 HLR 104 formulates a location request return result message (LocReq RR) 3 that serves as a response to the original LocReq message 2. LocReq RR message 3 includes routing information for the MSC servicing the called party in the GSM system. That is, the LocReq RR message 3 identifies GSM MSC 106 as an intermediary for reaching the called party. STP 100 forwards LocReq RR message 4 to IS-41 MSC 102. IS-41 MSC 102 receives the LocReq RR message 4 and uses the routing information contained therein to modify the routing label of the original IAM message and forwards the original IAM message as modified 5 to GSM MSC 106. Alternatively, a new IAM message including the routing information can be forwarded.
The message 5 is received by GSM MSC 106, which formulates and sends a send routing information (SRI) request message 6 to STP 100. STP 100 analyzes the message to determine the DN value associated with the called party, as well as service indication information contained in the message. STP 100 performs a lookup in an internal HLR routing table, determines that this message should be delivered to GSM HLR 108, and subsequently formulates and sends an SRI request message 7. Upon receipt of SRI request message 7, GSM HLR 108 examines the message and formulates an SRI-Acknowledge (SRI-Ack) message 8 that serves as a response to the original SRI message 7. SRI-Ack message 8 includes routing information to locate the mobile station of the called party. SRI-Ack message 9 is forwarded to GSM MSC 106 and is used by GSM MSC 106 to forward the call to the called party within the GSM service portion of the network(s). That is, GSM MSC 106 modifies the routing label of the original IAM message to address the message to an MSC that is currently serving the called party and forwards 10 the modified message to the MSC.
As can be appreciated from the migration scenario above, the signaling can become quite complex. In the example shown in FIG. 1, ten messages are required to determine that the called party has migrated and to forward the calls to the appropriate MSC. A large number of messages are required to set up a call, which also increases the call setup time.
Similar issues arise when considering the porting of subscribers from one service provider to another while keeping the same DN. For example, assuming for the moment the called party has been ported out, when a signaling message associated with a mobile subscriber that has been ported out is received, processing of the signaling message by one of the operator's HLR nodes is no longer necessary. As discussed above, despite the fact that the service provider's HLRs no longer store information needed to locate the mobile subscriber, conventional signaling techniques provide for the continued routing of signaling messages associated with the mobile subscriber to at least one of the service provider's HLR nodes for processing, as shown in FIG. 1. In particular, when STP 100 receives a signaling message associated with the ported out subscriber, the signaling message is subsequently routed to an HLR despite the fact that the needed information for that mobile subscriber is no longer maintained in the HLR. Such unnecessary routing constitutes an inefficient use of both routing and HLR database resources.
In other described signaling schemes, some or all of the signaling to and from the HLRs is reduced. Still, migration and portability are treated independently in these schemes. For example, commonly-assigned U.S. Pat. No. 6,662,017, the disclosure of which is incorporated herein by reference in its entirety, describes methods and systems for routing messages relating to ported subscribers. Commonly-assigned U.S. patent application Ser. No. 10/405,859, the disclosure of which is incorporated herein by reference in its entirety, describes methods and systems for migrating between application layer mobile signaling protocols. With migration and portability being treated independently, signal routing will be more complex than is necessary when subscribers can be migrated, ported, dual-mode, or any combination thereof.
Therefore, what is needed is systems and methods of efficiently redirecting signaling messages associated with migrated, ported, and/or dual-mode mobile subscribers among signaling nodes.